Gas-fired forced air heater



Feb,. 6, 1951 E. A. NORMAN, JR 2,540,280

GAS-FIRED FORCED AIR HEATER Filed Sept. 1, 1948 3 Sheets-Sheet l Figl.

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1951 E. A. NORMAN, JR

GAS-FIRED FORCED AIR HEATER 3 Sheets-Sheet 2 Filed Sept. 1, 1948 Fig. 5.

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1951 E. A. NORMAN, JR 2,540,280

GAS-FIRED FORCED AIR HEATER Filed Sept. 1, 1948 3 Sheets-Sheet 3 4: 4545 l I 28 {I I FAN Swn'cu NORMALLY 0 OPEN T. 1

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Patented Feb. 6, 1951 GAS-FIRED FORCED AIR. HEATER Edward A. Norman,Jr., Columbus, Ohio, assignor to Norman Products Company, Columbus,Ohio,

a corporation of Ohio Application September 1, 1948, Serial No. 47,282

9 Claims. 1

This invention relates to house heaters or furnaces and, moreparticularly, to automatically controlled heaters or furnaces of thegas-fired type in which air under forced flow is caused to travel overheat-exchanging surfaces.

Centralized house-heating furnaces of the forced air and gas-fired typesnow in general use possess characteristically relatively large cubicaldimensions. Normally the same require installation on the floor of abasement or furnace room which, in many small homes, renders their useobjectionable or prohibitive from a standpoint of space requirements;for example, housing in which conventional cellaror furnace rooms arenot provided. In meeting the heating requirements of such small homes,it is a common practice to utilize one or more room heaters, knowncommercially as space heaters, which ordinarily are incapable ofeffecting uniform heating of all rooms of such residential buildings ina manner comparable to heating obtained through the use of ductequippedcentral furnaces.

With these conditions, among others, under consideration, it is anobject of the present invention to provide an automatically controlledhouse-heating furnace of such lightweight and small physical dimensionsas to adapt the same for installation under the lower floorsofbasementless houses, in low attics, small closets, or suspended fromany suitable room ceiling or other overlying support.

Another object of the invention is to provide a lightweight compactfurnace unit of such construction as to enable the same to be readilyinstalled in presently built houses, as well as those undergoingconstruction, and which, following installation, will be disposed inout-of-the-way and space-saving locations.

It is another object of the invention to provide a gas-fired unit heateror furnace having a high heat output when the compactness andcomparatively small dimensions of the heater are taken intoconsideration.

With these and other objects and advantages in view, which will appearas the description proceeds, the invention consists in the novelfeatures of construction, combinations of elements and arrangements ofparts hereinafter more fully detailed and pointed out in the appendedclaims.

In the accompanying drawings:

Fig. 1 is a top plan view of a gas-fired heater or furnace constructedin accordance with the "resent invention;

Fig. 2 is a side elevational view thereof;

Fig. 3 is an end view from the cold air inletside of the heater orfurnace; v

Fig. 4 is an enlarged vertical longitudinal sectional view taken throughthe heater or furnace and showing the air circulating sociatedheat-exchanging tubes;

Fig. 5 is a horizontal sectional view, the plane fan and the asof whichbeing indicated by the line 5-5 of v Fig. 4; v

by the line 66 of Fig. 4;

Fig. 7 is a similar view, on the line 'l-'l of Fig. 4;

Fig. 8 is a detail horizontal sectional view on the line 8-8 of Fig. 2;

Fig. 9 is a sectional view on the line 9-9 of Fig. 7 and illustratingthe fan motor controlling switches;

Fig. 10 is a detail sectional view taken through one of burner tubes onthe plane indicated by the line l0--l 0 of Fig. 5;

Fig. 11 is a diagrammatic view disclosing the I electrical circuitsemployed in the automatic control of the heater;

Fig. 12 is a detail top plan view illustrating the heat-exchanging tubesand disclosing a means for varying the effective area of the open upperends of the tubes.

Referringmore particularly to the drawings, the numeral I designates theouter casing of my improved heater or furnace. Preferably, the casing isformed to provide a straight longitudinal duct of sheet metal, the wallsof which being suitably joined in rigidly connected relationship andinternally braced, the duct being substantially rectangular in itstransverse cross section. One end of the duct is provided with a coldair inlet 2, while the opposite end thereof is formed with a hot airoutlet 3. It will be understood that the inlet 2 may be joined withducts or pipes, not shown, for the return of air from the room or roomsof a house heated by the furnace, While the hot air outlet 3 may beconnected with pipes or ducts leading to the room or rooms to be heated.

In certain installations, the hot air outlet may be joined with ashutter-controlled hood 4 for directing heated air into a room to beheated, after the manner of a ceiling or wall-mounted unit heater. Thusin commercial buildings of the type involving one comparatively largeroom, the single hot air outlet provided by the hood 4 may be usedadvantageously. In house heating applications, however, theinlet 2 andthe outlet 3 are joined with associated ducts leading from the heater tothe house rooms to be heated thereby. The construction is thus flexiblein its adaptation to either type of heating.

Located in the casing I contiguous to the air inlet 2 thereof is anelectric motor 5 having the armature shaft 6 thereof provided with fanor blower blades 1, the latter being arranged for rotation in a shroud8. The motor 5 is preferably supported by means of eye members 9 whichcarry coil springs It], the eye members having their inner ends suitablyjoined with the frame of the motor and their outer ends connected withduct-carried brackets H. The motor is thus provided with a springsuspension by which vibration and noise incident to its operation areprecluded or minimized. The fanor blower serves to draw air into thecasing through the inlet 2 and positively advance the samelongitudinally of the casing for discharge through the outlet 3 thereof.

Between the fan or blower 1 and the outlet 7 3, the casing is providedinternally with heat-exchanging means embodying upper and lower boxingsl2 and I3 respectively. The lower boxing is formed to provide a burnerchamber M in which are positioned a pair of gas burners l5 havingslotted burner orifices 16. The burners are provided with elbows H whichextend laterally and externally of the casing along one side thereof.The open outer ends of these elbows are disposed in registration withapertured gas outlet heads or plugs l8 which are positioned in fittingsl9 joined with a gas-supplying pipe line 20. As the gas issues from theheads or plugs l8, the same is drawn into and mixed with air enteringthe operi outer ends of the elbows l1 and advanped through said elbowsto the burners proper, in order that active fuel combustion may takeplace at or immediately above the orifices 16 of the burners l5. Theburners are equipped with studs 21, as shown in Fig. 4, which arereceived in slots provided in bracket lugs 22 projecting inwardly fromthe walls of the burner chamber, in order to provide convenience in themounting and replacement of the burners.

Carried by and positioned vertically between the upper and lower boxingsl2 and I3 are relatively spaced heat-exchanging tubes 23. These tubesare in open communication at their lower ends-with the burner chamber l4and are so disposed as to register vertically with the slotted orificesl6 of the burners 15. At their upper ends, the tubes 23 are in opencommunication with a plenum chamber 24 provided by the upper boxing l2.Each of these tubes in horizontal cross section provides fiat parallelside walls 25 which are united at their ends by arcuate edge walls. 1

I have found that the heat-exchanging efflciency of these tubes issubstantially increased by bringing the side walls 25 thereof closertogether intermediately of their lengths, as indicated at 26, so thatthe passage for the burner gases formed by each tube is restrictedcross-sectionally in the region indicated at 26. This hourglassconfiguration of the tubes provides for a more effective wiping of theinner walls with the hot burner gases and the removal of heat therefromby the forced travel of air over the outer surfaces of said tubes. Thearrangement and configuration of the tubes contributes materially to thecompactness in design of the heater as a whole, providing for a highdegree of heat output, low stack temperatures and small physicaldimensions on the partof the outer casing.

, The plenum chamber communicates at one side of the heater with wastegas outlet collars 21 which support in connection with the casing a fluebox 28, the latter being provided with an outlet 29 leading to anatmospheric vent.

The heater or furnace is adapted to be automatically controlled inaccordance with the heat requirements of the room or rooms heatedthereby. Thus the pipe line 20 employed in supplying gas to the burnersI5 is provided ahead of the fittings IS with a normally closedsolenoidactuated valve 38. The field windings of the solenoid of thisvalve are arranged in a low voltage circuit disposed on the secondaryside of a transformer 3|, and included in this low voltage circuit is aroom-mounted thermostat 32. When a demand for heat exists in a room inwhich the thermostat is disposed, the thermostat, which may be of thecustomary bimetallic construction, operates to close a switch 33, thuscompleting the low voltage circuit and energizing the solenoid of thevalve 30 to open the latter, providing for normal gas flow to theburners ii to sustain active fuel combustion at required rates. When theheat demand has been satisfied, the thermostatic switch 33 opens andthesolenoid of the valve 30 is deenergized to arrest gas flow to theburners.

The transformer 3| has its primary side connected with conductors 34 and35 leading to a conventional source of electrical energy. Joined withthe conductor 35 is a normally open fan switch 36 which, as shown inFig. 7, is mounted on the upper tube boxing [2. This switch is joinedwith a conductor 31 which leads to the windings of the fan motor 5, andfrom the conductor 34, a conductor 38 extends to the other side of themotor windings. While the fan switch 36 may be of any suitableconstruction, the same in this instance has been shown as comprising asnap type bowed diaphragm 38 carrying contacts 40 which are adapted forengagement with sta tionary contacts 41 with which the conductors 35 and31 are joined.

It will be seen by this arrangement that after the burners 15 have beenin active operation for a predetermined period of time and the walls ofthe boxing l2 attain a desired temperature, the heating of such wallswill result in the transference of heat to the diaphragm 39, causing thelatter to quickly flex in a direction in which the contacts 40 thereofare brought into engagement with the contacts 4|, thereby completing thefan-motor circuit. In this manner, the operation of the fan iscontrolled from the temperature of the heat exchanger. When thethermostat calls for heat, the fan does not start until the heatexchanger is hot enough to deliver warm air, thus preventing theapparatus from circulating unheated air. Similarly, when the operationof the gas burners has been discontinued by the opening of thethermostatic switch, the fan motor continues to operate, blowing airacross the outer surfaces of the heat exchanger until the temperature ofthe heat exchanger drops to a point causing the diaphragm 39 to flex ina direction separating the contacts 40 and 4|.

As a safety feature, I employ a normally closed limit switch 42, whichis mounted on the boxing l2 contiguous to the fan switch 36. The limitswitch may be of substantially the same constructicn as the fan switch,having a bowed diaphragm 43 carrying contacts 44 which are normallyarranged in engagement with stationary contacts 45, the latter beingjoined with the conductor 35 leading to the primary side of thetransformer. The switch 42 remains closed under the normal operatingtemperatures of the heater, but in the event there should be failure onthe part of the fan motor to operate under prescribed temperatureconditions, the resulting overheating of the heat exchanger, whichincludes the boxing l2, will cause the diaphragm 43 to flex in adirection separating the contacts 44 and 45, thus interrupting the flowof current to the primary side of the transformer and deenergizing thecircuit of the solenoid valve. This arrests the flow of the combustiblegaseous fuel to the main burners IS. The pipe line ahead of the solenoidvalve may be provided with the usual pilot fittings 46 from which smallpipe lines 41 lead to pilot burners arranged adjacent to the mainburners l5, the pilot burners operating, as usual, to maintain low stagecombustion of fuel over the main burners to ignite fuel issu ing fromthe orifices i6 thereof.

In view of the foregoing, it will be seen that I'have provided a simpleand compact central heating system especially designed to meet theparticular heating needs of small homes and commercial buildings. Theapparatus can be easily and economically installed in all types ofbuildings, and no costly alteration expenses are involved to providesuch buildings with automatic central heating. As stated, the apparatusmay be suspended from a ceiling or under a floor, or disposed in acloset or back room. From such out-of-the-way locations, the heaterprovides a constant circulation of warmed air to all parts of a buildingcommunicating therewith, the apparatus being under thermostatic controlto secure desired room temperatures. In installations where duct work isnot used, the apparatus functions eificiently as a wall orceiling-mounted unit heater, and in this respect, is highly efiicient asa heating medium for store rooms and other commercial buildings.

I claim:

1. A unitary forced air heater comprising an elongated straightduct-like casing of substantially uniform cross-sectional areathroughout its length, said casing having a length dimensionsubstantially in excess of that of its width and height dimensions,there being an air inlet for cool air at one end of said casing and anoutlet for heated air at its opposite end, a heat exchanger arrangedwithin said casing between the inlet and outlet ends thereof, burnermeans carried by said casing for effecting the passage of hot combustiongases through said heat exchanger, said burner means having burnerorifices located below said heat exchanger, a fuel-air mixture conveyingconduit joined with said burner means, said conduit including an outerelbow disposed in parallel relation with and externally and laterally toone, side of said casing, said elbow and burner means being disposed inthe same horizontal plane, and a motor-driven fan mounted wholly withinthe confines of said casing between the air inlet end thereof and saidoutlet end thereof and operative to effect a forced passage of air drawninto said duct through the inlet end thereof over the heated surfaces ofsaid heat exchanger and thence outwardly of said casing through theoutlet end thereof while the air is passin through said casing in astraight longitudinal direction without change in its course of travel.

2. A forced air heater comprising an elongated straight duct-like casingof substantially uniform cross-sectional area throughout its length,said casing having a length dimension which is substantially in excessof that of its width and height dimensions, there being an air inlet forcool air at one end of said casing and an outlet for heated air at itsopposite end, a heat exchanger arranged within said casingintermediately of its inlet and outlet ends, said .exchanger includingupper and lower boxings'disposed within the confines of said casing, aplurality of vertically arranged relatively spaced fiat-sided tubesjoined at their ends with said boxings, gas burners positioned in thelower of said boxings, said burners having orifice-containing headsarranged below and in registry with open lower ends of said tubes, fuelmixture conveying conduits joined with said burner heads, said conduitshaving outer elbow portions extending parallel with and laterally andexternally of a side wall of said casing and substantially at rightangles to the portions of said conduits connected with said burnerheads, and motor-driven air-displacing means arranged wholly within thecasing between the air inlet end thereof and said heat exchanger.

3. A forced air heater as defined in claim 2, a gas-supplying pipe lineextending parallel to said casing and said outer elbows, and orificeprovided fittings carried by said pipe line, Said fittings having theorifices therein disposed in registry with the outer ends of saidelbows, whereby to deliver to said elbows a combustible mixture composedof a fuel gas drawn from said pipe line and atmospheric air.

' 4. A unitary forced air heater comprising an elongated straightductlike casing having a length dimension substantially in excess ofthat of its width and height'dimensions, there being an air inlet forcool air at one end of said casing and an outlet for heated air at itsopposite end,

a heat exchanger arranged within said casing between its inlet andoutlet ends, said exchanger including a plurality of vertically arrangedrelatively spaced tubes, a gas burner arranged below said tubes and inregistry therewith to project burning gases into the lower ends of saidtubes for upward passage through the tubes, means for collecting burnedgases discharged from the upper ends of said tubes and delivering thesame exteriorly of the casing for discharge to the atmosphere, a fuelmixture conveying conduit joined with said gas burner, said conduitincluding an outer elbow disposed in parallel relation with andexteriorly of and latetrally to one side of said casing, the outer endof said elbow being open, a fuel gas supply pipe extending parallel withthe outer side of said casing adjacent to said elbow, and an orificedfitting carried by said supply pipe, said fitting having the orificetherein disposed in registry with the open end of said conduit elbow toinject a mixture of fuel gas and atmospheric air into said elbow fortravel through said conduit to the combustion region of said burner, anda motor-driven fan positioned wholly within said casing between said airinlet and heat exchanger, said fan serving to effect a positive flow ofatmospheric air drawn into said casing over the heated surfaces of thetubes of said exchanger and the forced expulsion of the resultant heatedair through the outlet end of said casing,

maximum width and height dimensions, there being an air inlet for theentry of cool air at one end of said casing and an' outlet for thedischarge of heated air from the opposite end of the casing, a heatexchanger arranged within said casing between the inlet and outletcontaining ends thereof, said exchanger including upper and lowerboxings, a plurality of vertically arranged relatively spaced tubesjoined at their opposite ends with said boxings, gas burners positionedin said lower boxing in registry with the lower ends of said tubes, pipemeans extending parallel with and laterally and externally to an outerside of said casing for delivering a combustible mixture of fuel gas andair to said burners, and a motordrlven fan mounted wholly within theconfines of said casing between said inlet and said heat exchanger, saidfan serving to effect a positive advancement of air between and over theouter surfaces of said heat exchanger tubes and through said outlet.

6. A forced air heater as defined in claim 5 in combination withthermostatic switch means responsive to the temperature of the upper ofsaid heat exchanger boxings for delaying operation of said motor-drivenfan until the walls of said upper boxing attain a predeterminedoperating temperature.

7. A forced air heater as defined in claim 5, in combination with anelectrically actuated control valve for governing the flow of gaseousfuel from a source of supply to said burners, said valve including anoperating circuit, and a normally closed limit switch responsive to thetemperature of the walls of the upper boxing of said heat exchanger forautomatically opening the operating circuit of said valve and arrestinggas flow to said burner when the walls of said upper boxing attain atemperature in excess of a predetermined operating temperature.

8. A forced air heater comprising an elongated duct-like casing ofgenerally rectangular crosssectional configuration provided at one endwith a cold air inlet and at its opposite end with a hot 8 substantiallyin excess of that of its width and height dimensions; a heat exchangerarranged within said casing intermediately of its inlet and outlet ends,said exchanger including relatively spaced upper and lower boxingsdisposed within the confines of said casing and defining respectively aflue gas manifold and a burnerreceiving manifold, said exchanger alsoincluding a plurality of open-ended vertically arranged transverselyspaced flattened tubes extending between and communicating with saidboxings. said tubes being arranged in a row extending transversely orsaid casing; an elongated gaseous fuel burner positioned in the lowerboxing of said heat exchanger and extending transversely of said casing,said burner having flame orifices arranged below and in registrationwith the lower open ends of each of said tubes; a fuel-air supplyconduit communcating at one end with said burner and extending laterallyoutwardly from the lower boxing of said exchanger inthe plane of saidburner and terminating laterally and externally of a side wall of saidcasing; and motor-driven Number air outlet, said casing having a lengthdimension g.

air-displacing means positioned wholly within said casing forcirculating air first through the inlet of said casing, across said heatexchanger, and outwardly through the outlet of said casing.

9. A forced air heater as defined in claim 8 in combination with athermostatic switch positioned within said casing in thermal proximityto said heat exchanger and connected in series with said motor-drivenair-displacing means for delaying operation of said air-displacing meansuntil the temperature of said exchanger attains a given operatingtemperature.

EDWARD A. NORMAN, Jr.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date 2,190,349 Beam Feb. 13, 1940 2,213,656Pinkerton Sept. 3, 1940 2,262,158 Beam Nov. 11, 1941 FOREHGN PATENTSNumber Country I Date 103.295 Australia Feb. 17, 1938

